The long-term objectives of the proposed research are to understand the functional organization of the dorsal cochlear nucleus (DCN) for auditory information processing. The DCN is a complex neural structure containing an intricate neuropil. There are significant changes in the representation of the acoustic environment between the inputs and outputs of the DCN. The specific aims of this application are directed toward elucidating the roles of the various inputs to the DCN in producing the response characteristics of its output neurons. The effects on DCN prinicpal cells of the following inputs will be studied: Auditory nerve fibers, ventral cochlear nucleus principal cells that send axon collaterals to DCN, DCN interneurons, granule cells, and efferents to the DCN from more central auditory nuclei. These inputs will be studied using several methods: cross-correlation of spike trains, and improved cross-correlation method involving microstimulation of the units being studied, electrical stimulation of single neurons and whole fiber bundles, and pharmacological blockade of various inputs. The emphasis is on defining the major sources of excitatory and inhibitory input to DCN principal cells and the way in which these inputs interact with DCN interneurons.